Pleistocene-Holocene Crustal Deformation in the Far-Western Himalaya

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Pleistocene-Holocene crustal deformation in the far-Western Himalaya

Saptarshi Dey, IIT Gandhinagar, Gandhinagar-382355, India. [email protected]

Naveen Chauhan, Physical Research Laboratory, Ahmedabad- 380009, India. [email protected]

Debashis Nath, IIT Gandhinagar, Gandhinagar-382355, India. [email protected]

Niklas W. Schaaf, Christian Albrechts University of Kiel, Germany. [email protected]

Rasmus C. Thiede, Christian Albrechts University of Kiel, Germany. [email protected]

Vikrant Jain, IIT Gandhinagar, Gandhinagar-382355, India. [email protected]

Corresponding author email: [email protected]

Statement: This work has been submitted to Terra Nova in April 2021. This is a non-peer reviewed preprint submitted to EarthArXiv. If accepted, ‘peer-reviewed publication DOI’ link will be available on this webpage.

6/24/2021 1

2 3 Pleistocene-Holocene crustal deformation in the far-Western Himalaya

4 Saptarshi Dey1, Naveen Chauhan2, Debashis Nath1, Niklas W. Schaaf 3, Rasmus C. Thiede3,

5 and Vikrant Jain1

6 Corresponding author: Saptarshi Dey

7 Significance statement

8 Understanding the process and rates of crustal deformation on multi-millennial timescales is

9 important in seismic risk analysis. The crustal evolution of the Himalaya, imparted by the

10 ongoing intraplate convergence is highly debated and lacks data from specific areas which

11 have not witnessed high-magnitude seismicity in historical times. We present new

12 deformation rates from the western Himalaya to highlight that the intraplate convergence is

13 partitioned among several active structures at least since Late Pleistocene. Our work

14 underlines the existence of out-of-sequence fault activity in the western Himalaya and its’

15 mismatch with tectonic setting of the central Nepal Himalaya.

16 Abstract

17 We present new Late Pleistocene-Holocene shortening rates across the frontal fold-

18 and-thrust belt, namely as, the Sub-Himalaya (SH) from the far-western Himalayan sector of

19 Jammu. OSL-dated offset/ folded fluvial strath terraces suggest that the intraplate

20 convergence is partitioned among several active structures in the SH. Estimated cumulative

21 Late Pleistocene- Holocene shortening rate in the SH is ~9.5±1.3 mm/yr, which is ~70–75%

22 of the measured geodetic convergence rates. Our study invokes the existence of a ~350–400

23 km-long out-of-sequence fault-boundary within the SH which accommodates ~5.3±2.3

24 mm/yr shortening since Late Pleistocene-Holocene. Our study also highlights that ongoing

25 crustal shortening is not accommodated only at the toe of the Himalayan wedge.

26 1. Introduction

27 Quantification of ongoing crustal deformation of the Himalayan orogenic wedge is

28 fundamental for understanding deformation processes and improving assessment of future

29 seismic risks. Existing balanced cross-sections (e.g., Hirschmiller et al., 2014 and references

30 therein), Late Quaternary fault-slip estimates (e.g., Lave and Avouac, 2000; Thakur et al.,

31 2014; Vassallo et al., 2015; Dey et al., 2016b; Gavillot et al., 2016) or even geodetic

32 shortening rate estimates (e.g., Kundu et al., 2014; Banerjee and Burgmann, 2002;

33 Schiffmann et al., 2013) unanimously indicate that most of the crustal shortening in the

34 western Himalaya is accommodated in the frontal fold-and-thrust belt of the Himalaya,

35 known as the Sub-Himalaya (SH), since the Quaternary. The SH exposes an array of orogen-

36 parallel faults rooted to a low-angle basal detachment, known as the Main Himalayan Thrust

37 (MHT) (Ni and Barazangi, 1984) (Fig. 1). Studies on late Pleistocene-Holocene activity in

38 the western SH invoke the existence of multiple reactivated out-of-sequence structures in the

39 Sub-Himalaya which portray ~2-7 mm/yr slip rates as a result of recurring high-magnitude

40 seismic events triggered along the basal detachment (Thakur et al., 2014; Dey et al., 2016b;

41 Gavillot et al., 2016; Cortes Aranda et al., 2018). Surprisingly, historical seismicity (Bilham,

42 2019) and paleo-seismic investigations (Kumar et al., 2006; Kumhara and

43 Jayangondaperumal, 2013; Malik et al., 2015) reveal that some of these ‘active’ structures

44 show no activity on shorter timescales. Therefore, these ‘long-term active’ but ‘short-term

45 inactive’ structures pose greater seismic risks. This is one of the motivations to investigate

46 the ~ 200 km-long seismic gap between the seismic zones of the 2005 Kashmir Earthquake

47 and the 1905 Kangra Earthquake (Bilham, 2019) in the far-western Himalaya.

48 We used morphometric attributes, such as, longitudinal river profiles, channel width,

49 channel steepness to identify potentially-active structures and further quantified fault

50 displacement rates using chronologically-constrained uplifted fluvial strath surfaces. Offset/

51 folded fluvial straths mark differential rock uplift across potential structures (Lave and

52 Avouac, 2000; Dey et al., 2016; Cortes Aranda et al., 2017). Our work underlines two key

53 messages- 1. Only ~70–75% of the Himalayan shortening in the Jammu sector is

54 accommodated within the SH and the remaining must be accommodated in hanging wall of

55 the MBT and, 2. There exists a ~350–400 km long out-of-sequence fault boundary in the

56 western SH that accommodates ~30–50% of the total Himalayan shortening.

58 2. Geological background

59 The SH in Jammu Himalaya is ~70–80 km wide and exposes rocks of Murree

60 Formation and the Siwaliks (Fig. 1b). The SH units are folded and thrusted by multiple fault

61 systems (Fig. 1c) - the Murree Thrust (MT), the Tanhal Thrust (TT) (known as the Main

62 Riasi Thrust (MRT) in the Kashmir Himalaya) and the Mandili-Kishanpur Thrust (MKT)

63 (known as the Frontal Riasi Thrust (FRT) in the Kashmir Himalaya). The wedge margin fault

64 (Himalayan Frontal Fault, HFT) in this sector is blind and expressed by a growing anticline,

65 the Surain Mastgarh Anticline (SMA) (Fuchs, 1975; Raivermann et al., 1994; Gavillot et al.,

66 2018). The uplift of the MKT causes the tectonic damming, which forms the Udhampur

67 piggyback basin on its hanging wall (Gavillot et al., 2016; Malik and Mohanty, 2017). In

68 Table 1, we compiled the previously-published deformation rates from the Kashmir

69 Himalaya, Jammu Himalaya and the Kangra Recess. The FRT and JMT are the contemporary

70 structures of MKT in the neighboring fault segments (Table 1). The GPS-derived

71 convergence rate in Jammu sector is 13±1 mm/yr (Schiffman et al., 2013).

72 3. Methods and results

73 3.1. Field observation

74 The UB is dissected by the Tawi River and fluvial incision has sculpted at least six

75 levels of terraces. We mapped the fluvial terraces and measured their average height with

76 respect to the present base level using multi-point averaged hand-held GPS measurements

77 and high resolution DEM dataset. In the northern part of the UB, we found ~100m thick

78 sequence of fluvial boulders intercalated with discontinuous meter-thick sand-silt layers. The

79 southern part of the basin, however, is devoid of large-scale Late Pleistocene- Holocene

80 alluvium and the fluvial terraces are only capped by 1-3 m-thick veneer of alluvium. In the

81 hanging wall of the MKT, we recognize six different fluvial terrace levels (Fig.2a, 5a). We

82 named them T1-T6, according to the decreasing heights from the Tawi River (Fig. 4a).

83 Terrace levels T3-T6 are identified as straths as they only have 1-3 m thick alluvium atop the

84 tilted SH bedrock units.

85 Along the Ujh R. section (cf. Fig. 1c), we identified 3 levels of fluvial straths (U1, U2

86 and U3) (Fig. 4a). The U3 strath level is the most ubiquitous and is identified by a

87 continuous ~1–1.5 m-thick layer of light brown silt sitting atop the tilted bedrock strath (Fig.

88 2g, 6a). In the field we measured a change in height of the U3 strath with respect to the

89 fluvial base level between ~8 and 28 m over a distance of 20 km (Fig. 4b).

90 3.2. Morphometry

91 Longitudinal river profiles, steepness indices and channel width measurement are

92 often used as indicators of active tectonics (Seeber and Gornitz, 1983; Kirby and Whipple,

93 2012; Allen et al., 2013). We used 12.5m ALOS PALSAR terrain-corrected DEM for our

94 morphometric analysis. Details about morphometric indices and conditions applied are listed

95 in Appendix 1. Changes of morphometric indices across the MKT and other faults are shown

96 in Fig. 3 and 5.

97 Longitudinal profile of the Tawi River shows 2 major knickpoints KP1 and KP2

98 representing the upstream-head of steep river segments, ~4km and ~5 km upstream from the

99 MKT and MT, respectively (Fig. 5a). Channel width in the steep sections are lower (~40 m)

100 compared to the low-slope segments (> 80 m) or even in the UB (60–80 m) (Fig. 3b). The

101 steep segments are characterized by transient increase in normalized steepness indices (ksn)

102 values from <200 to ≥400 (Fig. 5c). Longitudinal profile of the Ujh R. doesn’t show any

103 knickpoints on the profile (Supplementary Fig. S2), but the channel width is systematically

104 low at the hinge-zone of the anticline (Supplementary Fig. S3).

105 3.3. Luminescence dating for estimation of terrace abandonment age

106 We applied optically-stimulated luminescence (OSL) dating technique to obtain the

107 timing of sedimentation above fluvial strath surfaces and interpret those as the maximum

108 abandonment ages of the fluvial strath levels exposed across the MKT. For that we sampled a

109 total of 9 samples from fine sand and silt layers in the thin veneer of alluvium exposed above

110 the bedrock straths along the Tawi and Ujh River. Information about OSL samples and their

111 stratigraphic significance are listed in Table 1. We opted for OSL double-SAR protocol for

112 equivalent dose (De) estimation (Thomsen et al., 2008) using 24 aliquots of each sample

113 (Supplementary Fig. S5). The dose rate was estimated using the online software DRAC

114 (Durcan et al., 2015) from the data of Uranium (U), Thorium (Th), and Potassium (K)

115 measured using α, β and γ counters. We opted for Central Age Model for estimation of mean

116 De (Bailey and Arnold, 2006).

117 In the hanging wall of MKT, samples TW-01 and TW-02 above the T3 strath surface

118 yield ages of ~24.1±1.5 kyr and 22.3±1.3 kyr, respectively, and match stratigraphic order

119 (Fig. 6a). Samples TW-03 (8.6±1.0 kyr) and TW-04 (9.6±0.7 kyr) were taken above the T5

120 and T4 terrace levels, respectively – even if the errors overlap and they yield the same age

121 and the ages match with stratigraphic order. On the footwall of the MKT, we have only one

122 OSL age from above the 55m-high-strath level, which yields a depositional age of 20.3±0.8

123 kyr (sample TW-05), therefore this represents T3 in the hanging wall. Sample TW-06, taken

124 ~27m above the regional base-level yield a depositional age of 9.7±0.3 kyr, and we correlate

125 this with terrace T4, the most well-preserved and regionally-extensive terrace level. Along

126 the Ujh River section, we have three OSL ages- two ages from the regionally most prominent

127 and best-preserved terrace level (U3), which we relate to T4 terraces along the Tawi river

128 (sample UJ-01: 10.2±0.7 kyr and UJ-02: 9.8±0.8 kyr) and one age from the top of U1 terrace

129 level (relatable to T2 in Tawi section) (sample UJ-03: 53±2 kyr) (Fig. 6a).

130

131 4. Discussion

132 In this section, we discuss the variability in bedrock incision rates and their

133 implications in crustal deformation and compare our results with previously-published

134 deformation rates for a regional overview of ongoing crustal deformation in the Western

135 Himalaya. But, first we discuss how variations in morphometric indices were used to identify

136 active structures.

137 4.1. Identification of active tectonics using morphometry

138 Knickpoint K1 (Fig.3a) is not lithologically-controlled. On the contrary, the dip of

139 bedrock units increases downstream from 30–35˚ to 45–50˚. The channel width decreases

140 (Fig. 3b) and the ksn value increases (Fig. 3c). Combining these observations, we propose

141 that the upstream and downstream part of the K1 may actually represent two ramp segments,

142 i.e., ramp 1 and ramp 2 and K1 represents the bend of two ramp segments at the surface. The

143 steeper ramp (ramp 2) has higher bedrock incision (at C2) than ramp 1 (at C1) (Fig. 3d). In

144 the MKT footwall, the bedrock incision is less than in the hanging wall (at C3, the height of

145 T4 strath is 31 m).

146 4.2. Variability in bedrock incision implies tectonic uplift

147 Fluvial strath terrace heights and their corresponding abandonment ages are used to

148 calculate fluvial incision rate across the MKT, TT and SMA (Table 3). We observe higher

149 incision rates in the hanging wall of the MKT (5.2±0.2 mm/yr) compared to the footwall

150 (2.5±0.2 mm/yr). Note that, the bedrock incision in the footwall of the MKT is driven by the

151 growth of the SMA. Similar higher incision rates are obtained on the hanging wall of the TT

152 (~ 7 mm/yr). Incision rates vary between 1–2.7 mm/yr across the SMA. In our previous study

153 in the Kangra Basin, we showed that terrace abandonment and fluvial incision in

154 intermontane piggyback basins can be triggered by a combination of tectonic and climatic

155 forcing (Dey et al., 2016a and 2016b). However, climatically-enforced fluvial incision would

156 warrant a uniform incision. Therefore, we infer the differential incision on hanging wall and

157 footwall side of the fault to be tectonically-driven.

158 4.3. Crustal shortening estimates across SH structures

159 Offset fluvial straths have been used to quantify rock uplift rates across active

160 structures. In Fig. 5a, we illustrate how terraces surface of T3-T5 are regionally distributed

161 across the MKT. Applying orthogonal profile projection method and considering height

162 uncertainty, we deduce 58±3 m and 30±2m offset across the ~21 kyr-old T3 terrace and ~10

163 kyr-old T4 terrace, respectively (Tawi River section). We interpret this offset as differential

164 uplift across the active fault and it can be equated to rock uplift on the fault-ramp (Dey et al.,

165 2016; Lave and Avouac, 2000). Using the mean terrace abandonment ages we further

166 calculated the differential uplift rate ranging 3.0±0.5 mm/yr (Fig. 5a). Similar profile

167 projection method was used in our previous study on the JMT (cf Fig. 7 in Dey et al., 2016b).

168 Assuming the dip of MKT-fault ramp to be 30–35˚, (using field data on structural orientation

169 of the ramp of the MKT and balanced cross-section (Gavillot et al., 2018)), this translates into

170 a shortening rate of 4.5±1.0– 5.1±0.9 mm/yr. Similar pattern of offset of the 10 kyr-old T4

171 surface is seen across the MT (Fig. 5b). The deduced shortening rate (using fault-ramp angle

172 of 60˚) is 1.6±0.2 mm/yr. In case of the SMA, the U3 terrace shows variation in bedrock

173 incision up to 8–28 m while, the same U3 level has a height of 4–5 m, away from the fold.

174 We calculated the uplift due to folding by taking the ‘undisturbed’ U3 height as baseline.

175 Horizontal component of shortening (Fig. 6b) due to active folding was calculated using the

176 fold geometry (Fig. 6c). Component of shortening on the southern and northern limb of SMA

177 are 1.8±0.1 mm/yr and 1.3 mm/yr, respectively. So, the tentative shortening rate across the

178 SMA is 3.1±0.1 mm/yr.

179 4.4. Regional significance of our study

180 The cumulative crustal shortening rate accommodated within the SH is 9.5±1.3

181 mm/yr. Assuming the geodetic convergence rates to be consistent over geologic timescales,

182 our results indicate that ~70-75% of the total Himalayan shortening is accommodated in the

183 SH since at least Late Pleistocene-Holocene. Published shortening rates on the FRT in the

184 Kashmir Himalaya is 4.5±1.5 mm/yr since 39 ka (Gavillot et al., 2016), while shortening on

185 the JMT in the Kangra Recess is 3.5–4.2 mm/yr since 32 ka (Thakur et al., 2014) or, 5.6±0.8–

186 7.5±1.1 mm/yr since 10 ka (Dey et al., 2016b). Their contemporary in the Jammu SH, the

187 MKT shortens at a rate of 4.5±1.0 –5.1±0.9 mm/yr which is within the range proposed by

188 aforementioned studies. Therefore, we propose that the FRT-MKT-JMT represent segments

189 of a single surface-rupture fault that runs orogen parallel for ~350–400 km and

190 accommodates ~30–50% of the total Himalayan shortening (5.3±2.3 mm/yr). This implies

191 that it is one of most active out-of-sequence fault since Late Pleistocene-Holocene in the

192 entire Himalaya. Nevertheless, our cumulative shortening rate estimate also hint that another

193 ~3–4 mm/yr shortening has to be accommodated to compensate geodetically-obtained

194 convergence rate. Till date we have not recognized more active faulting within the SH or the

195 MBT. But, fluvial incision at rates at ≥ 3 mm/yr within the Kishtwar Window (KW) over

196 similar timescales indicated that the shortening deficit is likely accommodated within the KW

197 (Dey et al., 2021, accepted).

198 5. Conclusions

199 Unpaired bedrock strath surfaces preserved along the Tawi and Ujh River document

200 differential uplift of the SH strata and most likely triggered by ongoing crustal shortening

201 across major fault systems. We conclude-

202 a. Shortening rate across the MKT and TT in the range of 4.7±1.2 mm/yr since ~20 ka

203 and 1.6±0.2 mm/yr since 10 ka, respectively.

204 b. Tentative Holocene shortening rate across the SMA is 3.1±0.1 mm/yr.

205 c. Cumulative shortening rate across the SH is 9.5±1.3 mm/yr which relates to ~70-75%

206 of the geodetic convergence rates estimated for the entire western Himalaya.

207 d. FRT-MKT-JMT is a ~350–400 km-long single out-of-sequence fault-boundary

208 accommodating 30–50% of the total Himalayan shortening. It is regionally the most-

209 active structure at least since late Pleistocene if not longer.

210 e. Up to 3–4 mm/yr crustal shortening may still be accommodated in the hanging wall

211 the MBT, most likely within the KW.

212

213 Acknowledgements

214 S. Dey is supported by DST-INSPIRE faculty research grant (grant

215 #DST/INSPIRE/04/2017/003278) from Department of Science and Technology, Govt. of

216 India at IIT Gandhinagar. N. Schaaf and R. Thiede acknowledge support by Deutsche

217 Forschungsgemeinschaft (DFG - TH 1317/9-1). We thank S. Das and C. Singh for logistic

218 support in the fieldwork. We also thank M. Biswas for helping in statistical error propagation

219 used in this study.

220

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410 Figures and Tables for the manuscript titled

411 Pleistocene-Holocene crustal deformation in the far-Western Himalaya

412 Figures

413

414

415 Figure 1: (a) A general overview map of the far-western Himalaya showing major tectonic

416 boundaries. The Late Pleistocene active structures are marked in yellow (except the MKT-JMT fault

417 line) along with Published Holocene shortening rates from nearby active structures (Vassallo et al.,

418 2015; Gavillot et al., 2016; Thakur et al., 2014; Dey et al., 2016). (b) Lithological map of the Jammu

419 Himalaya (modified after Steck, 2003 and Gavillot et al. 2018). The studied river sections of the Tawi

420 and the Ujh are marked with red boxes. The point X (marked by red circle) is the pour-point used for

421 longitudinal profile analysis shown in Fig. 3a. (c) Bedrock structural orientations along with field-

422 documented tectonic boundaries in the Jammu Himalaya. Letters refer to the locations of the field

423 photographs in Fig. 2. (d) Partially-balanced cross-section across the Jammu Himalaya along line AB

424 (cf. Fig. 1b) (modified after Gavillot et al., 2018). Our study emphasizes the difference between long-

425 term exhumation rates and active shortening rates on multi-millennial timescales [Abbreviations:

426 MRT- Main Riasi Thrust, FRT- Frontal Riasi Thrust, MKT- Mandili Kishanpur Thrust, MT- Murree

427 Thrust, JMT- Jwalamukhi Thrust, SMA- Surain Mastgarh Anticline, ST- Soan Thrust, JA- Janauri

428 Anticline, KT- Kotla Thrust, KW- Kishtwar Window.]

429

430 Figure 2: Field photographs, see Fig. 1c for locations. (a) Fluvial strath terraces preserved in

431 Udhampur Basin (UB) in the hanging wall of the MKT. (b) T4 strath above the ramp of the MKT

432 showing strong incision into Siwalik ‘bedrock’. (c) Fluvial strath levels exposed along the Tawi R. at

433 the southern margin of the UB (d) OSL-dated silty sand layer in the alluvium covering the Siwalik

434 ‘bedrock’ units – interpreted as being deposited shortly before fluvial bedrock incision initiated

435 resulting surface abandonment and terrace formation. (e) Fluvial sediment cover above the T4 strath.

436 (f) T4 strath in the footwall of the MKT. Please recognize the high morphology of the MKT hanging

437 wall seen in the background. (g) U3 strath level sculpted into middle Siwalik bedrock exposed along

438 the fluvial channel of the Ujh River – see Fig. 6.

439

440 Figure 3: (a) Longitudinal profile of the Tawi River across the MKT, upstream from point X (cf. Fig.

441 1b) showing two major knickpoints, K1 and K2. C1, C2 and C3 are river-flow perpendicular

442 topographic cross-sections indicated in a. (b) Bedrock channel width measurements along the profile

443 show a lowering of the channel width across the ramp segments (ramp 1 and ramp 2) of the MKT. ksn

444 values plotted against the longitudinal profile length show an increase across the ramp segments

445 corroborating with our field finding of stronger incision potential (steeper river gradient) in the

446 hanging wall of the MKT. (c) Schematic illustration of sub-surface structural orientations beneath the

447 UB, deduced from a previously-published balanced cross-section (Gavillot et al., 2018) and verified

448 with our own field measurements. We propose two ramp segments, Ramp 1 and Ramp 2 on the MKT,

449 which have higher dip angle than the flat fault segment located to the north. (d) Terrace and valley

450 length perpendicular profiles across the Tawi River at locations C1, C2 and C3 show differential

451 incision depth of T4. We relate the observed difference in terrace-heights to active faulting and uplift

452 of the MKT hanging wall, fostering fluvial incision in the hanging wall, as the river tends to

453 equilibrate its longitudinal river-profile. Therefore, we assume that the variation in terrace heights

454 documented in field can be used as a marker horizon to measure differential uplift across the major

455 fault system and subsequent re-adjustment of the fluvial network.

456

457 Figure 4: (a) Fluvial terrace map and its relative heights to present stem river of fluvial network of the

458 intramontane Udhampur Basin and surroundings. (b) River perpendicular topographic profile along

459 AA’ shows the mean terrace heights with respect to the present-day stem river in the hanging wall of

460 the MKT. (c) Across-river topographic profile along BB’ in the footwall of the MKT. Please note the

461 relative height difference of the same strath surfaces across the MKT. Dated straths and relative

462 heights are used for calculation of fault displacement rates – see Fig. 5.

463

464

465

466 Figure 5: (a) Longitudinal profile of the Tawi River across the MKT showing variation in strath

467 heights. Different strath levels are projected on the trace of MKT to quantify differential uplift across

468 the MKT (following the method described in Dey et al., 2016b, cf. Fig. 7). Terrace abandonment ages

469 are used to quantify uplift rate and shortening rate (assuming θ of the fault ramp to be 30–35˚) on the

470 MKT. The calculated dz value across KP1 is 15m. (b) Longitudinal profile of a tributary of the Tawi

471 River crossing the MT-TT fault-zone. Differential uplift of 27±3 m across MT is deduced from T4

472 terrace heights extracted from the DEM. Assuming the dip of the MT fault-ramp is ~ 60˚, this relates

473 to an estimated Holocene shortening rate of 1.6±0.2 mm/yr.

474

475 Figure 6: (a) Fluvial terrace heights (black values, in m) map along the Ujh River section. Note the

476 change in height of the U3 strath terrace across the SMA (see Photo in Fig. 2g). The average age of

477 the strath is 10.2±0.7 kyr. (b) Folded Siwalik topography and U3 terrace heights plotted along a swath

478 window of 4 km along AA’ (cf. Fig. 6a) show variability in U3 terrace heights along the river profile.

479 U3 terrace heights mimic the topography of the SMA, implying stronger incision rates (growth rate)

480 in the vicinity of the hinge. The component of crustal shortening at each terrace point is calculated

481 based on the differential bedrock incision (with respect to the unfolded strath height beyond the

482 wedge-margin) and orientation of the folded strata. (c) A schematic cross-section of the SMA along

483 Ujh River showing the structural orientation of the Siwalik strata based in our field data.

484

485

486 Tables

shortening Time Structures/domain rate/growth rate Study Area averaging (mm/yr) window (kyr) Main Riasi Thrust (MRT) ~6–7 Gavillot et al., 2016 Chenab ~100–40 Frontal Riasi Thrust ~3–6 Gavillot et al., 2016 Chenab ~39-0 (FRT) Medlicott Wadia Thrust ~11.2±3.8 Vassallo et al., 2015 Chenab ~14-0 (MWT) ~9±3.2 Vassallo et al., 2015 Chenab ~24-0 Surain-Mastargh Anticline (SMA) ~4.6 Gavillot, 2014 Chenab ~53-0 ~0.2–2.0 Jagtap et al., 2018 Jammu ~50- 7 Jwalamukhi Thrust 3.5–4.2 Thakur et al., 2014 Kangra ~32–30 (JMT) 5.6 ± 0.8 - 7.5 ± 1.1 Dey et al., 2016 Kangra ~10-0 Soan Thrust (ST) 3.0 Thakur et al., 2014 Kangra ~29-0 Himalayan Frontal Thrust ~6.0±0.5 Thakur et al., 2014 Kangra ~42-0 (HFT) 487

488 Table 1: Compilation of previously-published shortening rates on the active structures in the Western

489 SH. Note that FRT and JMT are contemporary to the MKT exposed in our study area. Please note the

490 discrepancy in growth rate estimates for the SMA between the studies.

Dose Central Long. U Th H O OD Sample Lat. (˚) K (%) 2 rate De (Gy) Age (˚) (ppm) (ppm) (%) (%) (Gy/kyr) (kyr)

TW-01 32.9137 75.1217 3.5±0.1 19.6±0.2 2.28±0.2 5 4.50±0.1 111±5.9 12 24.1±1.5

TW-02 32.9021 75.1375 3.3±0.1 15.8±0.1 2.62±0.2 6 4.55±0.2 101.5±5.2 13 22.3±1.3 TW-03 32.8908 75.1746 3.0±0.2 12.7±0.2 1.96±0.1 8 3.49±0.1 30.1±3.4 10 8.6±1.0 TW-04 32.8907 75.1488 3.5±0.1 9.5±0.1 1.98±0.1 10 3.31±0.1 31.9±2.3 9 9.6±0.7 TW-05 32.7489 75.1523 3.8±0.1 18.5±0.2 2.2±0.2 10 4.04±0.2 82.1±4.1 9 20.3±0.8 TW-06 32.8405 75.0258 3.4±0.1 9.5±0.4 2.0±0.1 9 3.72±0.1 36.9±3.0 14 9.7±0.7 UJ-01 32.4812 75.4348 3.5±0.1 14.2±0.3 2.1±0.1 8 3.50±0.1 37.2±3.1 12 10.6±0.8 UJ-02 32.5584 75.5467 3.4±0.1 9.5±0.4 2.0±0.1 8 3.72±0.1 36.0±3.0 14 9.8±0.8 UJ-03 32.5807 75.5314 3.9±0.2 14.1±0.1 1.7±0.1 6 3.10±0.1 165±6.1 7 53±2 491

492 Table 2: Details of OSL samples, elemental concentrations, dose rate, equivalent dose and central age

493 (after Bailey and Arnold, 2006).

Bedrock Incision/ Age Sample incision Uplift rate (kyr) (m) (mm/yr) MKT hanging wall TW-02 ~115 22.3±1.3 5.2±0.3 TW-04 ~52 9.6±0.7 5.4±0.4 TW-03 ~44 8.6±1.0 5.1±0.6 MKT footwall / SMA northern limb (Tawi) TW-05 ~55 20.3±0.8 2.7±0.1 TW-06 ~27 9.7±0.7 2.8±0.2 MKT footwall/ SMA northern limb (Ujh) UJ-02 23 9.8±0.8 2.3±0.2 UJ-03 70 53±2 1.3±0.1 SMA southern limb (Ujh) UJ-01 11 10.6±0.8 1.0±0.1 494

495 Table 3: Bedrock incision rates across the MKT measured from variable strath heights exposed along

496 the Tawi River.

497

498